Physicochemical Stability of Poly(lactide-co-glycolide) Nanocapsules Containing the Local Anesthetic Bupivacaine

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Self-Absorption and Luminescence Quantum Yields of Dye-Zeolite L Composites

Electronic absorption and fluorescence spectra based on transmission measurements of thin layers obtained from new perylene−zeolite L composites and new dye1,dye2−zeolite L sandwich composites, the latter acting as antenna systems, have been investigated and analyzed. The influence of extra- and intraparticle self-absorption on the spectral shape and fluorescence quantum yield is discussed in detail. Due to its intraparticle origin, self-absorption and re-emission can often not be avoided in organized systems such as dye−zeolite L composites where a high density of chromophores is a prerequisite for obtaining the desired photophysical properties. We show, however, that it can be avoided or at least minimized by preparing dye1,dye2−zeolite L sandwich composites where donors are present in a much larger amount than the acceptors because they act as antenna systems.

Surface modification of cellulose nanocrystals by grafting with poly(lactic acid)

The use of biopolymers obtained from renewable resources is currently growing and they have found unique applications as matrices and/or nanofillers in ‘green’ nanocomposites. Grafting of polymer chains to the surface of cellulose nanofillers was also studied to promote the dispersion of cellulose nanocrystals in hydrophobic polymer matrices. The aim of this study was to modify the surface of cellulose nanocrystals by grafting from L-lactide by ring-opening polymerization in order to improve the compatibility of nanocrystals and hydrophobic polymer matrices. The effectiveness of the grafting was evidenced by the long-term stability of a suspension of poly(lactic acid)-grafted cellulose nanocrystals in chloroform, by the presence of the carbonyl peak in modified samples determined by Fourier transform infrared spectroscopy and by the modification in C1s contributions observed by X-ray photoelectron spectroscopy. No modification in nanocrystal shape was observed in birefringence studies and transmission electron microscopy.

Cationic Bovine Serum Albumin (CBA) conjugated Poly Lactic-co-Glycolic Acid (PLGA) nanoparticles for extended delivery of methotrexate into brain tumor

Current treatment strategies for the treatment of brain tumor have been hindered primarily by the presence of highly lipophilic insurmountable blood-brain barrier (BBB). The purpose of current research was to investigate the efficiency of engineered biocompatible polymeric nanoparticles (NPs) as drug delivery vehicle to bypass the BBB and enhance biopharmaceutical attributes of anti-metabolite methotrexate (MTX) encapsulated NPs. The NPs were prepared by solvent diffusion method using cationic bovine serum albumin (CBA), and characterized for physicochemical parameters such as particle size, polydispersity index, and zeta-potential; while the surface modification was confirmed by FTIR, and NMR spectroscopy. Developed NPs exhibited zestful relocation of FITC tagged NPs across BBB in albino rats. Further, hemolytic studies confirmed them to be non-toxic and biocompatible as compared to free MTX. In vitro cytotoxicity assay of our engineered NPs on HNGC1 tumor cells proved superior uptake in tumor cells; and elicited potent cytotoxic effect as compared to plain NPs and free MTX solution. The outcomes of the study evidently indicate the prospective of CBA conjugated poly (D,L-lactide-co-glycolide) (PLGA) NPs loaded with MTX in brain cancer bomber with amplified capability to circumvent BBB.

Physicochemical Stability of Poly(lactide-co-glycolide) Nanocapsules Containing the Local Anesthetic Bupivacaine

This paper describes the preparation of poly(DL-lactide-co-glicolide) (PLGA) nanocapsules as a drug carrier system for the local anesthetic bupivacaine. The system was characterized and its stability investigated. The results showed a size distribution with a polydispersity index of 0.12, an average diameter of 148 nm, a zeta potential of -43.5 mV and an entrapment efficiency of 75.8%. The physicochemical properties of polymeric nanocapsule suspensions (average diameter, polydispersity, zeta potential and drug association efficiency) were evaluated as a function of time to determine the formulation stability. The formulation did not display major changes in these properties over the time, and it was considered stable up to 120 days of storage at room temperature. The results reported here which refer to the initial characterization of these new formulations for the local anesthetic bupivacaine show a promising potential for future in vivo studies.

Estudo inicial da degradação in vivo de poli(L-co-D,L ácido lático), sintetizado em laboratório, aplicado como prótese tibial em coelhos

The copolymer poly (L-co-D,L lactic acid), PLDLA, has gained prominence in the field of temporary prostheses due to the fact that their time of degradation is quite compatible with the requirement in the case of osseous fracture. In this work the in vivo degradation of devices from copolymer, as a system of plates and screws, used in fixation of the tibia of rabbits was studied. The devices were implanted in 15 adult rabbits, albinos, New Zealand race, and they were used as control devices of alloys of titanium (Ti-6Al-4V/ V grade). The use of copolymers, synthesized in the laboratory, was tested in the repair of fracture in rabbits'tibias, being assessed in the following times: 2 weeks, 2 months and 3 months. Morphological analysis of tissue surrounding the plate and screw system, for 2 weeks of implantation, showed the presence of osteoblasts, indicating a pre bone formation. After 2 months there was new bone formation in the region in contact with the polymer. This bone growth occurred simultaneously with the process of PLDLA degradation, invading the region where there was polymer and after 3 months there was an intense degradation of the copolymer and hence greater tissue invasion compared to 2 months which characterized bone formation in a region where the polymer degraded. The in vivo degradation study of the devices for PLDLA by means of histological evaluations during the period of consolidation of the fracture showed the efficiency of plate and screw system, and it was possible to check formation of bone tissue at the implantation site, without the presence of inflammatory reaction

Reconstruction of mandibular segmental defects using the guided-bone regeneration technique with polylactide membranes and/or autogenous bone graft: A preliminary study on the influence of membrane permeability

Purpose: Bone maintenance after mandibular reconstruction with autogenous iliac crest may be disappointing due to extensive resorption in the long term. The potential of the guided-bone regeneration (GBR) technique to enhance the healing process in segmental defects lacks comprehensive scientific documentation. This study aimed to investigate the influence of polylactide membrane permeability on the fate of iliac bone graft (BG) used to treat mandibular segmental defects. Materials and Methods: Unilateral 10-mm-wide segmental defects were created through the mandibles of 34 mongrel dogs. All defects were mechanically stabilized, and the animals were divided into 6 treatment groups: control, BG alone, microporous membrane (poly L/DL-lactide 80/20%) (Mi); Mi plus BG; microporous laser-perforated (15 cm(2) ratio) membrane (Mip), and Mip plus BG. Calcein fluorochrome was injected intravenously at 3 months, and animal euthanasia was carried out at 6 months postoperatively. Results: Histomorphometry showed that BG protected by Mip was consistently related to larger amounts of bone compared with other groups (P <= .0001). No difference was found between defects treated with Mip alone and BG alone. Mi alone rendered the least bone area and reduced the amount of grafted bone to control levels. Data from bone labeling indicated that the bone formation process was incipient in the BG group at 3 months postoperatively regardless of whether or not it was covered by membrane. In contrast, GBR with Mip tended to enhance bone formation activity at 3 months. Conclusions: The use of Mip alone could be a useful alternative to BG. The combination of Mip membrane and BG efficiently delivered increased bone amounts in segmental defects compared with other treatment modalities. (C) 2008 American Association of Oral and Maxillofacial Surgeons.

Development of composite particles for pulmonary delivery

In this work, biocompatible and biodegradable poly(D-L-lactide-co-glycolide) (PLGA) microparticles with the potential for use as a controlled release system of vaccines and other drugs to the lung were manufactured using supercritical CO2, through the Supercritical Assisted Atomization (SAA) technique. After performing a controlled variance in production parameters (temperature, pressure, CO2/solution flow ratio) PLGA microparticles were characterized and later used to encapsulate active pharmaceutical ingredients (API). Bovine serum albumin (BSA) was chosen as model protein and vaccine, while sildenafil was the chosen drug to treat pulmonary artery hypertension and their effect on the particles characteristics was evaluated. All the produced formulations were characterized in relation to their morphology (Morphologi G3 and scanning electronic microscopy (SEM)), to their physical-chemical properties (X-ray diffraction (XRD, differential scanning calorimetry (DSC), Fourier transform infrared (FTIR)) and aerodynamic performance using an in vitro aerosolization study – Andersen cascade impactor (ACI) - to obtain data such as the fine particle fraction (FPF) and the mass median aerodynamic diameter (MMAD). Furthermore, pharmacokinetic, biodegradability and biocompatibility tests were performed in order to verify the particle suitability for inhalation. The resulting particles showed aerodynamic diameters between the 3 and 5 μm, yields up to 58% and FPF percentages rounding the 30%. Taken as a whole, the produced microparticles do present the necessary requests to make them appropriate for pulmonary delivery.

High performance electromechanical actuators based on ionic liquid/poly(vinylidene fluoride)

Due to the increasing need of low voltage actuators, independent from electrochemical processes, electroactive actuators based on poly(vinylidene fluoride) composites with 10, 25 and 40 % of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C2mim] [NTf2], ionic liquid are prepared by solvent casting and melting. We show that the charge structure of [C2mim] [NTf2] induces the complete piezoelectric -phase crystallization of the PVDF within the composite and decreases its crystallinity fraction significantly. [C2mim] [NTf2] also works as a plasticizer of PVDF, reducing the elastic modulus down to 12 % of the initial value. Moreover, the composites show significant displacement and bending under applied voltages of 2, 5 and 10 Vpp. The displacement and bending of the composite membranes are also evaluated as a function of [C2mim] [NTf2] content and sample thickness. Increasing amounts of ionic liquid result in larger deformations independently of the applied voltage.

A biodegradable drug delivery system for the treatment of postoperative inflammation

Cataract surgery is often performed in patients suffering from associated pathologies. Our goal is to develop a biodegradable drug delivery system (DDS) combined with the artificial intraocular lens (IOL). DDS were manufactured using poly(D,L-lactide-co-glycolide), or PLGA, and were loaded with triamcinolone acetonide (TA). The loading capacity was approximately 1050 microg of TA per DDS. The higher the molecular weight of PLGA (34,000, 48,000 and 80,000Da), the slower was the release of TA in vitro. Cataract surgery was performed on the right eye of rabbits. IOL was inserted with (i) no DDS, (ii) unloaded DDS PLGA48000, (iii) one loaded DDS PLGA48000, (iv) two loaded DDS. The number of inflammatory cells and the protein concentration were measured in the aqueous humor (AH). Unloaded DDS showed good ocular biocompatibility. One DDS PLGA48000 loaded with TA significantly reduced postoperative ocular inflammation. Two loaded DDS PLGA48000 was even more effective in inhibiting such inflammation. On long-term observation (days 63 and 84), reduction of inflammation could be obtained by insertion of one DDS PLGA48000 and a second DDS PLGA80000. Therefore, our "all in one" system is very promising since it could replace oral treatment and reduce the number of intraocular injections

Tuning the immune response of dendritic cells to surface-assembled poly(I:C) on microspheres through synergistic interactions between phagocytic and TLR3 signaling.

The artificial dsRNA polyriboinosinic acid-polyribocytidylic acid, poly(I:C), is a potent adjuvant candidate for vaccination, as it strongly drives cell-mediated immunity. However, because of its effects on non-immune bystander cells, poly(I:C) administration may bear danger for the development of autoimmune diseases. Thus poly(I:C) should be applied in the lowest dose possible. We investigated microspheres carrying surface-assembled poly(I:C) as a two-in-one adjuvant formulation to stimulate maturation of monocyte-derived dendritic cells (MoDCs). Negatively charged polystyrene microspheres were equipped with a poly(ethylene glycol) corona through electrostatically driven surface assembly of a library of polycationic poly(l-lysine)-graft-poly(ethylene glycol) copolymers, PLL-g-PEG. Stable surface assembly of poly(I:C) was achieved by incubation of polymer-coated microspheres in an aqueous poly(I:C) solution. Surface-assembled poly(I:C) exhibited a strongly enhanced efficacy to stimulate maturation of MoDCs by up to two orders of magnitude, as compared to free poly(I:C). Multiple phagocytosis events were the key factor to enhance the efficacy. The cytokine secretion pattern of MoDCs after exposure to surface-assembled poly(I:C) differed from that of free poly(I:C), while their ability to stimulate T cell proliferation was similar. Overall, phagocytic signaling plays an important role in defining the resulting immune response to such two-in-one adjuvant formulations.

Surface assembly of poly(I:C) on PEGylated microspheres to shield from adverse interactions with fibroblasts.

By expressing an array of pattern recognition receptors (PRRs), fibroblasts play an important role in stimulating and modulating the response of the innate immune system. The TLR3 ligand polyriboinosinic acid-polyribocytidylic acid, poly(I:C), a mimic of viral dsRNA, is a vaccine adjuvant candidate to activate professional antigen presenting cells (APCs). However, owing to its ligation with extracellular TLR3 on fibroblasts, subcutaneously administered poly(I:C) bears danger towards autoimmunity. It is thus in the interest of its clinical safety to deliver poly(I:C) in such a way that its activation of professional APCs is as efficacious as possible, whereas its interference with non-immune cells such as fibroblasts is controlled or even avoided. Complementary to our previous work with monocyte-derived dendritic cells (MoDCs), here we sought to control the delivery of poly(I:C) surface-assembled on microspheres to human foreskin fibroblasts (HFFs). Negatively charged polystyrene (PS) microspheres were equipped with a poly(ethylene glycol) (PEG) corona through electrostatically driven coatings with a series of polycationic poly(L-lysine)-graft-poly(ethylene glycol) copolymers, PLL-g-PEG, of varying grafting ratios g from 2.2 up to 22.7. Stable surface assembly of poly(I:C) was achieved by incubation of polymer-coated microspheres with aqueous poly(I:C) solutions. Notably, recognition of both surface-assembled and free poly(I:C) by extracellular TLR3 on HFFs halted their phagocytic activity. Ligation of surface-assembled poly(I:C) with extracellular TLR3 on HFFs could be controlled by tuning the grafting ratio g and thus the chain density of the PEG corona. When assembled on PLL-5.7-PEG-coated microspheres, poly(I:C) was blocked from triggering class I MHC molecule expression on HFFs. Secretion of interleukin (IL)-6 by HFFs after exposure to surface-assembled poly(I:C) was distinctly lower as compared to free poly(I:C). Overall, surface assembly of poly(I:C) may have potential to contribute to the clinical safety of this vaccine adjuvant candidate.

Intravitreous injection of PLGA microspheres encapsulating GDNF promotes the survival of photoreceptors in the rd1/rd1 mouse.

PURPOSE: To evaluate the potential delay of the retinal degeneration in rd1/rd1 mice using recombinant human glial cell line-derived neurotrophic factor (rhGDNF) encapsulated in poly(D,L-lactide-co-glycolide) (PLGA) microspheres. METHODS: rhGDNF-loaded PLGA microspheres were prepared using a water in oil in water (w/o/w) emulsion solvent extraction-evaporation process. In vitro, the rhGDNF release profile was assessed using radiolabeled factor. In vivo, rhGDNF microspheres, blank microspheres, or microspheres loaded with inactivated rhGDNF were injected into the vitreous of rd1/rd1 mice at postnatal day 11 (PN11). The extent of retinal degeneration was examined at PN28 using rhodopsin immunohistochemistry on whole flat-mount retinas, outer nuclear layer (ONL) cell counting on histology sections, and electroretinogram tracings. Immunohistochemical reactions for glial fibrillary acidic protein (GFAP), F4/80, and rhodopsin were performed on cryosections. RESULTS: Significant delay of rod photoreceptors degeneration was observed in mice receiving the rhGDNF-loaded microspheres compared to either untreated mice or to mice receiving blank or inactivated rhGDNF microspheres. The degeneration delay in the eyes receiving the rhGDNF microspheres was illustrated by the increased rhodopsin positive signals, the preservation of significantly higher number of cell nuclei within the ONL, and significant b-wave increase. A reduction of the subretinal glial proliferation was also observed in these treated eyes. No significant intraocular inflammatory reaction was observed after the intravitreous injection of the various microspheres. CONCLUSIONS: A single intravitreous injection of rhGDNF-loaded microspheres slows the retinal degeneration processes in rd1/rd1 mice. The use of injectable, biodegradable polymeric systems in the vitreous enables the efficient delivery of therapeutic proteins for the treatment of retinal diseases.

Preparação, caracterização e estudos de biodegradação de blendas à base de PDLLA e PVP

Poly(D,L-lactide), PDLLA, is a polymer with potential applications in medical, environmental, and pharmaceutical areas. Despite its versatility, the hydrophobicity limits its applications. To overcome this problem, one strategy is the preparation of blends with hydrophilic polymers such as poly(vinylpyrrolidone), PVP. In this study, we report the preparation and characterization of blends based on PDLLA and PVP and the biodegradation studies by the Sturm test. It was observed that the components of the blends PDLLA/PVP are thermodynamically immiscible, however the biodegradation is faster than that of pure PDLLA.

CARACTERIZAÇÃO E AVALIAÇÃO IN VITRO DE NANOCOMPÓSITOS DE POLI (L-ÁCIDO LÁTICO) E NANOTUBOS DE CARBONO DE PAREDES MÚLTIPLAS PURIFICADOS

Carbon nanotubes (CNT) have been studied for biomedical applications due to their unique properties. However, pristine CNT have structural features and impurities that can cause toxicity to biological systems. In this work, we describe a method to purify multiwalled carbon nanotubes (MWCNT) by chemical modification and subsequent attachment of hydroxyl and carboxyl groups to improve dispersion and to decrease toxic effects. Nanocomposites from poly (L-lactic acid) (PLLA) and nanotubes were produced by the solvent casting method and characterized and evaluated for cytocompatibility with Vero cells. The nanocomposite interactions with Vero cells demonstrated that the cells were able to adhere and sustain proliferation and showed favorable cytocompatibility. In vitro studies also revealed an increase in fibroblast cell viability in the nanocomposites, compared with neat PLLA.